New cancer therapies with novel mechanisms and functions are needed to treatpatients with different cancers. Virotherapy is a good scenario for such treatment. The advantages of virotherapy include the potential lack of cross resistance with standard therapies and the ability to cause tumor destruction by numerous mechanisms. Oncolytic virus not only possesses unique mechanisms of action that are distinct from other treatment modalities, its self-perpetuating nature provides an ideal platform for therapeutic transgenic insertion. In this review article, a variety of oncolytic viruses in cancer gene therapy will be described.